An optical vortex is a light wave that has characteristic properties such as an angular momentum which derives from a phase singularity, and a doughnut-shaped intensity distribution.
A representative example of the optical vortex is Laguerre-Gaussian beam (See the undermentioned NON-PATENT DOCUMENT 1).
Laguerre-Gaussian beam is an intrinsic solution of a wave equation in a cylindrical coordinate system.
It satisfies the periodic boundary condition that the phase rotates by an integer multiple of 2 pi around the rotation center when the beam propagates for every 1 wavelength.
Therefore, it is possible to express the magnitude of the angular momentum by using the quantum number L (L=1, 2, 3 . . . ).
The wave surface of an optical vortex has a helical shape. An orbital angular momentum is generated in the direction which is given by vector difference between the normal direction of a wave surface and the propagation direction of an optical vortex.
Further, an optical vortex can be utilized for a light manipulation which uses light radiation pressure, a microscope with high resolution which uses phase singularity, an optical vortex ablation processing which actively uses orbital angular momentum etc. Therefore, future industrial applications of the optical vortex are highly expected.
As prior art of oscillating an optical vortex, there is a device which is described in below-described non-patent document 1.